The invention is in the field of finishing interior walls, and specifically relates to finishing the edges at intersections where two or three walls meet, either as an inside corner or as an outside corner.
Currently, any intersection between two drywall planes, which is an obtuse or "outside" intersection, is covered with a metallic strip which defines a corner bead and has orthogonally oriented flanges which are nailed to the adjacent drywall, with the central bead falling over the intersection itself. These strips have been used for many years and are in widespread current use. Because of their construction however, they have certain inherent defects. One of the major defects is the fact that even though they are galvanized or otherwise coated with a non-corrosive coating, the strips will sometimes corrode or rust anyway, and bleed through the overlying plaster or mud, creating an unsightly appearance.
Another drawback of the metallic strips is inherent in the fact that the malleable metal from which they are made has a very poor memory, and is subject to being dented or wrinkled, after which it is difficult to straighten to produce a smooth finish. Because of the rough handling to which most of the material at a work site is subjected, it is not uncommon for the strips to be wrinkled, dented and perhaps twisted, thus rendering them either unuseable, or useable only to produce a slightly inferior end result.
Additionally, the metal strips are used in large quantities in construction, and can up to a considerable cost. A means of reducing this cost would find a warm reception in the buidling industry because although the cost savings on one strip may be not be significant, the enormous numbers of the strips that are used would provide a substantial savings to builders of even a single dwelling, not to mention a whole tract or large office building.
Attempts have been made to create other types of strips which are made of plastic rather than metal to resolve some of the above-stated problems. Among these are those described in U.S. Pat. No. 2,114,044 issued to W. L . Bonnell; U.S. Pat. No. 3,712,003, issued to Edward C. Hallock et al., and U.S. Pat. No. 4,315,390 to Michael Schafsma. These attempts toward resolving the problem have produced edge beads which by and large lie underneath the drywall at the intersection between two drywall panels. This approach does not conform to present techniques, whereupon the bead is put on after the drywall has already been put in place, and this requires the re-education of construction workers, who tend to be set in their ways.
Another approach is taken in U.S. Pat. No. 4,012,878 issued to Robert T. Ellingston. This strip can be put in place after the drywall is in place. It is characterized by having an air pocket and a double layer for providing resilience to impact, so that the underlying wall corner or edge is not damaged from impact. However, not only does the double-walled construction not lending itself to ease in manufacture by extrusion, but it could also somewhat problematic in that the paint and plaster or mud which is applied over the trim would be cracked and would tend to flake because of the deformation of the underlying strip when it is impacted.
There is a need, therefore for a simple, plastic strip which is designed to be easily extruded, and which is provided with accompanying corner pieces to accomodate the most commonly encountered intersections of edges into corners, which includes both inside outside corners, and corners with two or three lines defined by intersecting wall planes.